Prepreg Out-Time Tracker Worksheet
Prepreg is perishable: every hour outside the freezer consumes a measured share of its usable out-life, and a roll that exceeds its limit can produce porous or poorly tacked laminates. This worksheet gives you a per-roll ledger that adds up exposure automatically and shows what is left before a layup starts.
| Roll or kit ID | Material and spec | Lot | Date out of freezer | Out-life limit (hr) | Out-time before this session (hr) | This session (hr) | Cumulative out-time (hr) | Out-life remaining (hr) | Out-life used | Disposition | |
|---|---|---|---|---|---|---|---|---|---|---|---|
45.5 | 434.5 | 9.5% | |||||||||
126 | 354 | 26.3% | |||||||||
311 | 49 | 86.4% | |||||||||
244 | -4 | 101.7% | |||||||||
6 | 474 | 1.3% |
Out-life limits differ by material and are set by the supplier datasheet or your material specification, not by this sheet. The values shown are examples only. Record every exit from the freezer in hours, including thaw time before the bag is opened if your spec counts it. A negative remaining value means the limit was exceeded and the material must be dispositioned under your nonconformance process. This worksheet is a record aid and does not replace the controlled form required by your quality system.
Link out-time to ERP material issues
Optional: see how freezer issue and return transactions can drive roll-level out-time and expiry alerts.
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How to use the tracker
Create one row per roll or kit when it first leaves the freezer. Record the material, lot and the out-life limit from the datasheet in hours. At the end of each session, enter the hours the material was out. If the roll was used before, put the previous total in the prior column. The sheet adds them, shows cumulative out-time, the hours remaining and the percent of out-life used. Choose a disposition for each row, and export to Excel or PDF for the shift record. Totals highlight the shortest remaining out-life across the list, which is the roll the supervisor should schedule first.
- Start the clock when the sealed bag leaves cold storage, unless your spec says otherwise.
- Log thaw time and layup time as separate sessions if different areas apply different rules.
- Put a hard stop at a chosen percent of out-life, for example 80%, to leave margin for cure.
What out-life means
Datasheets quote two related limits. Out-life, or out-time, is the cumulative time at room temperature that the prepreg can sit before use while keeping its tack and flow. Mechanical life is the longer window within which a part can be laid up, bagged and cured before the resin advancement hurts quality. Shelf life is the time the sealed material can be stored at freezer temperature, often quoted at minus 18 C. Cumulative exposure includes every freeze and thaw cycle, which is why a running total beats a single timestamp.
Reading the output
A positive remaining value means the roll is still inside its limit; the percent column is the same information normalized. In the example the glass roll has exceeded its limit by four hours and its disposition is scrap or material review. Anything between 80% and 100% should be flagged for first use or for a tight schedule. Compare the shortest remaining value with the cure cycle time and the layup duration: a roll with 20 hours left cannot support a 30-hour layup and bag.
Common mistakes
The most frequent mistake is losing the prior exposure when a partial roll goes back into the freezer, so the next user starts the count at zero. Another is applying one limit to all materials; different resin systems and tapes have very different values, and out-time at humid or warm shop temperatures can effectively consume more life than the sheet shows. Never extend a limit without a documented material review. If your spec requires time-at-temperature integration, this sheet is a simplification and you need a thermal log.
Frequently Asked Questions
What is prepreg out-time?
Out-time is the cumulative time prepreg spends outside freezer storage at room temperature. It is tracked because resin advances slowly even at ambient conditions, reducing tack and flow. Each material has a maximum out-life, usually stated in the datasheet in hours or days.
How do I record out-time when material goes back to the freezer?
Add the hours of the finished session to the roll's running total and write that total in the prior column the next time it is pulled. Mark each roll with a label or tag showing the total so the number travels with the material.
Is out-time the same as mechanical life?
No. Out-time limits how long the prepreg can be at room temperature before cure, while mechanical life describes the working window for layup and bagging before the resin has advanced too far. Check which one your specification controls, and keep your cure plan inside the smaller number.
Can I extend the out-life limit?
Only through your documented material review or engineering disposition, usually backed by test data such as tack, flow and short beam shear on aged material. Do not extend limits informally on the shop floor.
If material receiving and issue transactions are in your ERP, Netray can link freezer issues and returns to roll-level out-time automatically, so the traveler shows live remaining life.
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Guides
- Prepreg Out-Time Tracking: Keeping Expired Material Off the ToolHow to track prepreg out-time and shelf life: freezer pulls, thaw, kitting, cumulative exposure, labels and ERP records that keep expired material off the tool.
- Quality Records a Composites Shop Needs for AS9100 and NADCAPWhat quality records a composites shop needs for AS9100 and NADCAP audits: material control, process records, NCRs, calibration and traceability from part to lot.